1. Technical Field
The present invention relates to a method for manufacturing a semiconductor device, and particularly relates to the method for manufacturing the semiconductor device that can be suitably used in the step of forming an oxide film on a semiconductor wafer by an ALD (Atomic Layer Deposition) method.
2. Background Art
In recent years, with an increase of high-density and multilayer interconnection of a semiconductor DRAM device, film formation at a low temperature is required, and further a capacitor material having excellent planarity of a surface, recess filling property, and step coverage property, and high dielectricity (k) is required. Materials such as HfO2 (k=30), ZrO2 (k=25) are used as the capacitor material having higher dielectricity than that of a conventional Si3N4 (k=7).
A film formation method of HfO2 includes a sputtering method, a MOCVD (Metal organic CVD) method, and an ALD method, and among these methods, the ALD method capable of performing the film formation at a low temperature and having high step coverage property has been focused in recent years, and has been developed energetically.
The ALD (Atomic Layer Deposition) method, which is one of the CVD (Chemical Vapor Deposition) method, is a technique of supplying reactive gas, being at least two kinds of raw materials used in film formation, onto an Si wafer alternately one by one, making this reactive gas adsorbed on a silicon wafer by one atomic unit, and performing film formation by using a surface reaction.
As a hafnium raw material used in the ALD film formation method, an organic material of Hf such as Hf (O-tBu)4 (Hafnium tertiary butoxide:Hf [OC(CH3)3]4), Hf (MMP) (Tetrakis 1-methoxy 2-methyl 2-propoxy hafnium:Hf [OC(CH3)2CH2OCH3]4), Hf(Net2)4 (Tetrakis diethyl amino hafnium:Hf [N(C2H5)2]4), Hf(NMeEt)4 (Tetrakis ethylmethyl amino hafnium:Hf [N(CH3)(C2H5)]4), and a chloride material such as HfCl4 are used. Note that C2H5 is abbreviated to H5, and CH3 is abbreviated to Me.
In addition, H2O and ozone (O3), or oxygen excited by plasma is used as an oxide material.
However, when a thin film such as a HfO2 film is formed by flowing the aforementioned materials alternately into a processing chamber, a film thickness in a wafer central part is decreased by using a pattern wafer having a trench (groove) structure, thus deteriorating a step coverage or deteriorating the step coverage of the HfO2 film by the number of pattern wafers in 1 batch (called a loading effect).
In order to improve such step coverage and loading effect, a supply amount of the hafnium raw material is increased or supplying time is increased, thus improving the step coverage and the loading effect. However, an increase of the film forming time is invited to deteriorate throughput, and a cost involved in the raw material is increased by the increase of consumption of the raw material, to invite a deterioration of COO (Cost of ownership: manufacturing cost per one wafer).